Pre-lubrication and soak-back system for a machine

ABSTRACT

A lubrication system for an engine is disclosed. The lubrication system may have an oil pump configured to lubricate the engine. The lubrication system may also have a valve configured to direct oil from the oil pump to a fuel pump associated with the engine. The lubrication system may further have a controller. The controller may be configured to determine an operating speed of the engine. The controller may also be configured to adjust the valve to selectively direct the oil to the fuel pump based on the operating speed.

TECHNICAL FIELD

The present disclosure relates generally to a lubrication system and, more particularly, to a pre-lubrication and soak-back system for a machine.

BACKGROUND

An internal combustion engine includes numerous metallic parts, which move relative to each other in very close proximity. To reduce friction between the moving parts, the engine typically includes a lubrication system, which supplies oil to lubricate the moving parts. The lubrication system usually includes an engine-driven oil pump, which draws oil from a sump and circulates the oil through the engine.

When an engine remains inoperative for a long time, however, oil in the engine drains into the sump because of gravity. To prevent damage to the engine's moving parts, it may therefore be necessary to pre-lubricate the engine before turning it on. Typically, an auxiliary oil pump, driven by an electric motor, draws oil from the sump and circulates the oil to pre-lubricate the engine. Once the engine turns on, however, the auxiliary oil pump turns off to conserve energy and the engine-driven oil pump continues to circulate oil through the engine. Other components associated with the engine, such as turbochargers and/or fuel pumps, may also require pre-lubrication when the engine remains inoperative for a long time.

Some of these components may require oil for lubrication and cooling even after the engine has been turned off. For example, hot exhaust exiting from the engine propels the turbochargers in modern engines. Although the bearings and other moving parts in these turbochargers can withstand the high temperature of engine exhaust, they require oil for cooling and lubrication. When the engine is on, oil supplied by the engine-driven oil pump lubricates and cools the turbochargers. When the engine is turned off, however, the engine-driven pump can no longer supply oil to the turbochargers. The auxiliary pump may supply oil to cool and lubricate the turbochargers as they decelerate from their operating speed and come to a complete stop. The process of lubricating and cooling the turbochargers and/or other components after the engine has been turned off is called soak-back. To ensure that the engine and associated components are adequately lubricated, it is necessary to detect when the engine is about to start and when it has been turned off, and accordingly start the auxiliary oil pump to supply oil for pre-lubrication or soak-back.

One attempt to address the problems described above is disclosed in U.S. Pat. No. 5,894,825 of Duerr that issued on Apr. 20, 1999 (“the '825 patent”). In particular, the '825 patent discloses a supplemental lubrication system to pre-lubricate an engine and its accompanying turbocharger and post-lubricate (i.e. perform soak-back of) the turbocharger. The '825 patent discloses a two-directional pump, which directs oil flow to either or both the engine and the turbocharger. The '825 patent also discloses that the pump may be driven by a three phase AC motor with input from a control module. The '825 patent further discloses that during engine and turbocharger pre-lubrication, the pump delivers a portion of the oil to the engine and another portion to the turbocharger. In addition, the '825 patent discloses that during post-lubrication, after the engine has been turned off, the pump supplies oil only to the turbocharger.

Although the '825 publication discloses a system for pre-lubrication and soak-back, the disclosed system may still be problematic. For example, at low engine speeds, the engine-driven oil pump may not generate sufficient oil pressure to supply oil to lubricate all the components of the engine. Adding another oil pump to supplement the engine-driven oil pump at low engine speeds may increase the complexity of the system and may make the system more expensive to implement and maintain.

The lubrication system of the present disclosure solves one or more of the problems set forth above and/or other problems in the art.

SUMMARY

In one aspect, the present disclosure is directed to a lubrication system for an engine. The lubrication system may include an oil pump configured to lubricate the engine. The lubrication system may also include a valve configured to direct oil from the oil pump to a fuel pump associated with the engine. The lubrication system may further include a controller. The controller may be configured to determine an operating speed of the engine. The controller may also be configured to adjust the valve to selectively direct the oil to the fuel pump based on the operating speed.

In another aspect, the present disclosure is directed to a method of operating a machine. The method may include supplying oil for lubrication, using a first oil pump associated with the machine. The method may also include lubricating an engine associated with the machine using the oil. The method may further include starting the engine. The method may also include determining an operating speed of the engine. In addition, the method may include adjusting a valve to selectively direct the oil from the first oil pump to a fuel pump associated with the engine based on the operating speed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial illustration of an exemplary disclosed machine;

FIG. 2 is a schematic of an exemplary disclosed lubrication system for the machine of FIG. 1;

FIG. 3 is a flow chart illustrating an exemplary disclosed method of lubrication performed by the lubrication system of FIG. 2 during engine startup;

FIG. 4 is a flow chart illustrating an exemplary disclosed method of lubrication performed by the lubrication system of FIG. 2 during engine operation; and

FIG. 5 is a flow chart illustrating an exemplary disclosed method of lubrication performed by the lubrication system of FIG. 2 after the engine has been turned off.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary embodiment of a machine 10. For example, as shown in FIG. 1, machine 10 may be a locomotive designed to pull rolling stock. Machine 10 may have a platform 12. A plurality of wheels 14 may be configured to support platform 12. Wheels 14 may also be configured to engage a track 16. Each wheel 14 may have a traction motor (not shown) associated with it. The traction motors may drive wheels 14 to propel machine 10 in a forward or rearward direction.

Machine 10 may have an engine 18 mounted on platform 12. Engine 18 may be configured to propel machine 10. For example, engine 18 may be configured to drive one or more generators (not shown), which may generate power to drive the one or more traction motors. Although FIG. 1 depicts one engine 18, it is contemplated that machine 10 may have more than one engine 18. In an exemplary embodiment as shown in FIG. 1, engine 18 may be lengthwise aligned on platform 12 along a travel direction of machine 10. One skilled in the art will recognize, however, that engine 18 may be located in tandem, transversally, or in any other orientation on platform 12.

FIG. 2 illustrates an exemplary disclosed lubrication system 20 for machine 10. As shown in FIG. 2, lubrication system 20 may include sump 30, first oil pump 32, first manifold 40, second manifold 50, third manifold 60, and controller 90. Lubrication system 20 may also include first and second filters 34, 94 and first, second, third, fourth, and fifth check valves 102, 104, 106, 108, and 110. Lubrication system 20 may supply oil for lubrication of engine 18, fuel pump 52, exhaust gas recirculation (EGR) valve arrangement 70, turbocharger arrangement 80, and other components associated with engine 18. Additionally, a second oil pump 92 may be associated with engine 18.

Sump 30 may be a tank or other enclosure for storing and/or collecting oil. Alternatively, sump 30 may be an oil pan placed underneath engine 18 to store and/or collect oil. First oil pump 32 may be connected to sump 30 via passageway 31. First oil pump 32 may draw oil from sump 30 via passageway 31 and pump it via passageway 33 to first manifold 40. First filter 34 may be disposed in passageway 33 between first oil pump 32 and first manifold 40 to filter the oil supplied by first oil pump 32. It is contemplated that lubrication system 20 may include one or more first filters 34 to filter the oil. It is also contemplated that first filter 34 may be disposed in passageway 31 to filter the oil before it enters first oil pump 32. Oil may flow from first manifold 40 to second manifold 50 via passageway 41, from first manifold 40 to third manifold 60 via passageway 43, and from first manifold 40 to engine 18 via passageway 45.

First oil pump 32 may be driven by an electric motor (not shown). Alternatively, first oil pump 32 may be driven by a dedicated engine (not shown). Unlike first oil pump 32, second oil pump 92 may be driven by engine 18. Alternatively engine 18 may drive a generator (not shown). Power from the generator may be used to drive a motor (not shown) configured to drive second oil pump 92.

Second oil pump 92 may draw oil from sump 30 via passageway 93 and pump oil to various components associated with engine 18 via passageway 95. Passageway 95 may merge with passageway 45 connecting first manifold 40 to engine 18. Second oil pump 92 may pump oil to fuel pump 52 and EGR valve arrangement 70 via passageway 97, to turbocharger arrangement 80 via passageway 99, and to engine 18 via passageway 45. First, second, and third check valves 102, 104, and 106 may prevent oil pumped by second oil pump 92 from flowing backwards in passageways 41, 43, and 45, respectively, towards first manifold 40. Similarly, fourth and fifth check valves 108 and 110 may prevent oil pumped by first oil pump 32 from flowing backwards in passageways 97 and 99, respectively, towards engine 18. It is contemplated that lubrication system 20 may include one or more of first, second, third, fourth, and fifth check valves 102, 104, 106, 108, and 110.

Second filter 94 may be disposed in passageway 45 to filter the oil supplied by first oil pump 32 or second oil pump 92. It is contemplated that lubrication system 20 may include one or more second filters 94 to filter the oil. It is also contemplated that second filter 94 may be disposed in passageway 93 to filter the oil before it enters second oil pump 92. Although FIG. 2 depicts only a single first oil pump 32 and a single second oil pump 92, it is contemplated that lubrication system 20 may have any number of first and second oil pumps 32, 92. Similarly, it is contemplated that lubrication system 20 may employ one or more first and second filters 34, 94 and/or additional filters located elsewhere in lubrication system 20 to filter the oil as it circulates within lubrication system 20.

First manifold 40 may include first control valve 42, which may receive oil from first oil pump 32 via passageway 33. First control valve 42 may be adjusted to direct a first flow of oil to second manifold 50 via passageway 41. First manifold 40 may also include second control valve 44, which may receive oil from first oil pump 32 via passageway 33. Second control valve 44 may be adjusted to direct a second flow of oil to third manifold 60 via passageway 43. In addition, first manifold 40 may include third control valve 46, which may receive oil from first oil pump 32 via passageway 33. Third control valve 46 may be adjusted to direct a third flow of oil to engine 18 via passageway 45.

The first, second, and third flows of oil may be equal or unequal. In one exemplary embodiment, the first, second, and third flows of oil may be determined based on diameters of passageways 41, 43, and 45, respectively. In another exemplary embodiment, the first, second, and third flows of oil may be determined by selectively adjusting first, second, and third control valves 42, 44, and 46, respectively. Although FIG. 2 depicts first, second, and third control valves 42, 44, and 46 as disposed within first manifold 40, it is contemplated that first, second, and third control valves 42, 44, and 46 may be located outside first manifold 40. It is also contemplated that lubrication system 20 may include first, second, and third control valves 42, 44, and 46, and may not include second manifold 50. Further, although FIG. 2 depicts second control valve 44 located below first control valve 42 and third control valve 46 located below second control valve 44, it is contemplated that first, second, and third control valves 42, 44, and 46 may be located in any spatial relationship with respect to each other.

First control valve 42 may be a proportional type valve having a valve element movable to regulate a flow of coolant through passageway 41. The valve element in first control valve 42 may be operable to move between a flow-passing position and a flow-blocking position. In the flow-passing position, first control valve 42 may permit substantially all of the oil from first oil pump 32 to flow through passageway 41 to second manifold 50. In an intermediate position in between the flow-passing position and flow-blocking position, first control valve 42 may permit some of the oil to flow to second manifold 50 while diverting the remaining portion back to sump 30 via an oil flow return passageway (not shown). And in the flow-blocking position, first control valve 42 may completely block oil from flowing to second manifold 50. Second and third control valves 44 and 46 may operate in a similar manner.

Alternatively, first, second, and third control valves 42, 44, 46 may each be two-position solenoid valves. Energizing first, second, and third control valves 42, 44, 46 of this exemplary embodiment may switch each of the first, second, and third control valves 42, 44, 46 from a flow-passing position to a flow-blocking position, or vice-versa. In this exemplary embodiment, the first flow of oil may be directed from first oil pump 32 to second manifold 50 by opening first control valve 42 and closing second and third control valves 44, 46. The second flow of oil may be directed from first oil pump 32 to third manifold 60 by opening second control valve 44 and closing first and third control valves 42, 46. The third flow of oil may be directed from first oil pump 32 to engine 18 by opening third control valve 46 and closing first and second control valves 42, 44.

Second manifold 50 may receive the first flow of oil from first manifold 40 and selectively distribute it to fuel pump 52 and EGR valve arrangement 70. For example, second manifold 50 may help direct a first portion of the first flow of oil to fuel pump 52 via passageway 51. Oil from fuel pump 52 may flow via passageway 71 and return to sump 30 via passageway 93. Although FIG. 2 depicts only one fuel pump 52, it is contemplated that more than one fuel pump 52 may supply fuel to engine 18. It is also contemplated that second manifold 50 may supply oil to some or all fuel pumps 52. Second manifold 50 may also help direct a second portion of the first flow of oil to EGR valve arrangement 70 via passageway 57. The first and second portions of the first flow of oil may be equal or unequal. Second manifold 50 and/or passageways 51 and 57 may include additional control valves (not shown) to control and direct the first and second portions of the first flow of oil.

EGR valve arrangement 70 may include first EGR valve 72 and second EGR valve 74. The second portion of oil may be supplied to first EGR valve 72 and second EGR valve 74 via passageways 53 and 55, respectively. Lubrication system 20 may include additional control valves (not shown) or check valves (not shown) to control the flow of oil to each of first and second EGR valves 72, 74. Oil flowing to first and second EGR valves 72, 74 via passageways 53, 55, respectively, may be used to activate first and second EGR valves 72, 74.

First and second EGR valves 72, 74 may be hydraulically activated valves. For example first and second EGR valves may each have an outer body 76 and a piston 78 configured to move along a longitudinal axis of outer body 76. A small amount of oil may flow through a gap 79 between outer body 76 and piston 78. This small amount of oil may be directed to passageway 93 via passageways 73 and 75. Although FIG. 2 depicts only one each of first and second EGR valves 72, 74, it is contemplated that EGR valve arrangement 70 may include any number of first and second EGR valves 72, 74.

Third manifold 60 may receive the second flow of oil from first manifold 40 and selectively distribute it to components within turbocharger arrangement 80. For example, third manifold 60 may help direct a first portion of the second flow of oil to first turbocharger 82 via passageway 61. Third manifold 60 may also help direct a second portion of the second flow of oil to second turbocharger 84 via passageway 63. In addition, third manifold may help direct a third portion of the second flow of oil to third turbocharger 86 via passageway 65. The first, second, and third portions of the second flow of oil may be equal or unequal. The first, second, and third portions of the second flow of oil may flow via passageways 81, 83, 85, respectively, and return to sump 30 via passageway 93. Third manifold 60 may include additional control valves (not shown) or check valves (not shown) to control and direct the first, second, and third portions of the third flow of oil. First, second, and third turbochargers 82, 84, 86 may be configured to supply compressed air to engine 18. Although FIG. 2 depicts only one of each of first, second, and third turbochargers 82, 84, 86, it is contemplated that turbocharger arrangement 80 may include any number of first, second, and third turbochargers 82, 84, 86.

Engine 18 may receive the third flow of oil from first manifold 40 via passageway 45. The third flow of oil from engine 18 may flow via passageway 91 and return to sump 30 via passageway 93.

Controller 90 may be in communication with first oil pump 32 and first, second, and third control valves 42, 44, 46. Controller 90 may also be in communication with engine 18. In addition, controller 90 may be in communication with a variety of sensors, for example, pressure sensors, speed sensors, temperature sensors, etc., which may communicate parameters such as a pressure of the oil exiting second oil pump 92, a speed of engine 18, and/or pressure and temperature of oil or fuel entering and leaving various components of engine 18.

Controller 90 may be configured to control operation of first, second, and third control valves 42, 44, 46. For example, controller 90 may cause first control valve 42 to move from a fully open first position to a fully closed position. It is also contemplated that controller 90 may cause first control valve 42 to be partially open to selectively supply a desired flow of oil to second manifold 50. Controller may be configured to control operation of second and third control valves 44 and 46 in a similar manner.

Controller 90 may control first oil pump 32 and first, second, and third control valves 42, 44, 46 to supply oil to engine 18 and other components in lubrication system 20. For example, controller may determine whether engine 18 is on. Controller 90 may determine whether engine 18 is on in many ways. For example, controller 90 may monitor a flow rate of fuel being supplied to engine 18, or a speed of rotation of a crankshaft of engine 18. Controller 90 may also monitor a temperature or pressure of fuel, coolant, exhaust, or other components and fluids within the engine to determine whether the engine is on. One skilled in the art would recognize that controller 90 may use signals from many different kinds of sensors to determine whether engine 18 is on or off.

When engine 18 is on, controller 90 may determine an operating speed E_(S) of engine 18. As used in this disclosure, the operating speed may refer to a speed of a crankshaft of engine 18, for example, in revolutions per minute or in any other appropriate unit of measurement known in the art. Alternatively, operating speed may be related to a speed of travel of machine 10. Additionally or alternatively, operating speed may be related to a speed of rotation of wheels 14 of machine 10.

Controller 90 may compare the operating speed of engine 18 to a threshold operating speed E_(TH). When the operating speed of engine 18 is less than the threshold operating speed, controller 90 may adjust first control valve 42 to direct oil from first oil pump 32 to fuel pump 52 and EGR valve arrangement 70 via second manifold 50. For example, controller 90 may allow more oil to flow from first manifold 40 to second manifold 50 at relatively higher operating speeds of engine 18 compared to at relatively lower operating speeds of engine 18. Thus, controller 90 may help ensure that fuel pump 52 is lubricated at low operating speeds of engine 18, at which second oil pump 92 may not be able to generate sufficient oil pressure to supply oil to fuel pump 52.

In one exemplary embodiment, when controller 90 determines that the operating speed of engine 18 is less than the threshold operating speed, controller 90 may fully open first control valve 42 and close second and third control valves 44, 46 to direct the first flow of oil to fuel pump 52 and EGR valve arrangement 70. Controller 90 may also adjust additional control valves and/or check valves to direct a first portion of the first flow of oil to fuel pump 52 and direct a second portion of the first flow of oil to first and second EGR valves 72, 74. When, however, controller 90 determines that the operating speed of engine 18 exceeds the threshold operating speed, controller 90 may close first control valve 42 and turn off first oil pump 32, allowing oil from second oil pump 92 to flow to fuel pump 52 for lubrication. In one exemplary embodiment, the threshold operating speed may be 300 revolutions per minute.

Controller 90 may also control first, second, and third control valves 42, 44, 46 to direct oil from first oil pump 32 to other components of machine 10. For example, controller may open third control valve 46 and close first and second control valves 42, 44 to direct oil from first oil pump 32 to engine 18. Thus, when engine 18 has been inoperative for a long time, controller 90 may direct oil to pre-lubricate engine 18 using first oil pump 32 before turning on engine 18. Similarly, controller 90 may open second control valve 44 and close first and third control valves 42, 46 to direct oil from first oil pump 32 to pre-lubricate first, second, and third turbochargers 82, 84, 86 before turning on engine 18. Controller 90 may also open first control valve 42 and close second and third control valves 44, 46 to direct oil from first oil pump 32 to pre-lubricate fuel pump 52 before turning on engine 18.

Controller 90 may also control first oil pump 32 and first, second, and third control valves 42, 44, 46 to perform soak-back operations when engine 18 is turned off. As used in this disclosure, soak-back refers to lubrication and cooling of components of machine 10 after engine 18 has been turned off. For example, when engine 18 has been turned off, controller 90 may turn on first oil pump 32. Controller 90 may also open second control valve 44 and close first and third control valves 42, 46 to direct oil from first oil pump 32 to first, second, and third turbochargers 82, 84, 86. Controller 90 may help ensure that oil is circulated to lubricate and cool first, second, and third turbochargers 82, 84, 86 for a sufficient amount of time until they come to a complete stop from their operating speed.

Controller 90 may embody a single microprocessor or multiple microprocessors, field programmable gate arrays (FPGAs), digital signal processors (DSPs), etc. that include a means for controlling an operation of lubrication system 20 in response to signals received from first oil pump 32, first, second, and third control valves 42, 44, 46, and various sensors. Numerous commercially available microprocessors can be configured to perform the functions of controller 90. It should be appreciated that controller 90 could readily embody a microprocessor separate from that controlling other machine-related functions, or that controller 90 could be integral with a machine microprocessor and be capable of controlling numerous machine functions and modes of operation. If separate from the general machine microprocessor, controller 90 may communicate with the general machine microprocessor via data links or other methods. Various other known circuits may be associated with controller 90, including power supply circuitry, signal-conditioning circuitry, actuator driver circuitry (i.e., circuitry powering solenoids, motors, or piezo actuators), communication circuitry, and other appropriate circuitry.

An exemplary operation of lubrication system 20 will be described next.

INDUSTRIAL APPLICABILITY

The disclosed lubrication system may be used in any machine or power system application where it is beneficial to pre-lubricate components of the machine before turning on an engine of the machine or to perform soak-back after the engine has been turned off. The disclosed lubrication system may find particular applicability with machines or power systems, which require supplemental lubrication at low engine operating speeds when an engine-driven oil pump may be unable to supply oil for lubrication of all desired components. The disclosed lubrication system may provide an improved method for lubricating the machine components throughout an operating speed range of the engine without the need for additional oil pumps.

FIG. 3 illustrates an exemplary method, which may be performed by lubrication system 20 during engine start up. Controller 90 may monitor and receive signals from the engine and sensors (Step 122). For example, controller 90 may monitor and receive signals from engine 18 and a variety of temperature, pressure, flow, speed, and other sensors. Controller 90 may determine whether an engine start signal has been received (Step 124). When controller 90 determines that an engine start signal has been received (Step 124, Yes), controller 90 may determine time t for which engine was off (Step 126). For example, controller 90 may determine the total amount of time t for which engine 18 had been off before an engine start signal was received. When controller 90 determines, however, that an engine start signal has not been received (Step 124, No), controller 90 may return to step 122.

After determining the time t in step 126, controller 90 may start first oil pump 32 (Step 128). Controller 90 may determine whether the engine was off for t>t_(OFF) (Step 130). For example, controller 90 may compare time t with a threshold amount of time t_(OFF) to determine whether engine 18 was off for an amount of time t, which was greater than the threshold amount of time t_(OFF). When controller 90 determines that the engine was off for t>t_(OFF) (Step 130, Yes), controller 90 may open third control valve 46 and close first and second control valves 42, 44 (Step 132). First oil pump 32 may lubricate the engine for time t₁ (Step 134). For example, controller 90 may keep third control valve 46 open to allow oil from first oil pump 32 to flow through and lubricate engine 18 for a first amount of time t₁. Controller 90 may then proceed to step 136. Returning to step 130, when controller 90 determines, however, that the engine was not off for t>t_(OFF) (Step 130, No), controller 90 may also proceed to step 136. In step 136, controller 90 may open second control valve 44 and close first and third control valves 42, 46 (Step 136). First oil pump 32 may lubricate turbochargers for time t₂ (Step 138). For example, controller 90 may keep second control valve 44 open to allow oil from first oil pump 32 to flow through and lubricate first, second, and third turbochargers 82, 84, 86 for a second amount of time t₂.

After time t₂ has elapsed, controller 90 may open first control valve 42 and close second and third control valves 44, 46 (Step 140). First oil pump 32 may lubricate fuel pump 52 for time t₃ (Step 142). For example, controller 90 may keep first control valve 42 open to allow oil from first oil pump 32 to flow through and lubricate fuel pump 52 for a third amount of time t₃. After time t₃ has elapsed, controller may start engine 18 (Step 144). Note that, controller 90 may keep first control valve 42 open to supply oil to lubricate fuel pump 52 even after engine 18 has been started. In one exemplary embodiment the threshold amount of time t_(OFF) may be about 48 hours. In another exemplary embodiment the first amount of time t₁ may be about 5 minutes, the second amount of time t₂ may be about 2 minutes, and the third amount of time t₃ may be about 2 minutes.

FIG. 4 illustrates an exemplary method of lubrication performed by the lubrication system 20 during operation of engine 18. As illustrated in FIG. 4, controller 90 may determine operating speed E_(s) of engine 18 (Step 146). Controller 90 may determine whether E_(s)>E_(TH) (Step 148). For example, controller 90 may compare the operating speed Es of engine 18 with a threshold operating speed E_(TH). When controller 90 determines that E_(s)>E_(TH) (Step 148, Yes), controller 90 may determine whether first oil pump 32 is on (Step 150). When controller 90 determines that first oil pump is on (Step 150, Yes), controller 90 may stop first oil pump 32 (Step 152). Controller 90 may then return to step 146. Returning to step 150, when controller 90 determines, however, that first oil pump is not on (Step 150, No), controller 90 may also return to step 146.

Returning to step 148, when controller 90 determines that E_(s) is not >E_(TH) (Step 148, No), controller 90 may determine whether first oil pump 32 is on (Step 154). When controller determines that first oil pump 32 is on (Step 154, Yes), controller 90 may open first control valve 42 and close second and third control valves 44, 46 (Step 156). When controller 90 determines, however, that the first oil pump 32 is not on (Step 154, No), controller 90 may start first oil pump 32 (Step 158), before proceeding to step 156. In step 156, first oil pump 32 may supply oil to lubricate the fuel pump and activate EGR valves (Step 160). For example, first oil pump 32 may supply oil to lubricate fuel pump 52 and activate first and second EGR valves 72, 74. After completing step 160, controller 90 may return to step 146. Thus, by starting first oil pump 32, at low operating speeds of engine 18, controller may ensure that sufficient oil is supplied to fuel pump 52 and first and second EGR valves 72, 74, without the need for additional oil pumps.

FIG. 5 illustrates an exemplary method of lubrication performed by the lubrication system 20 when engine 18 is turned off As further illustrated in FIG. 5, Controller 90 may monitor and receive signals from the engine and sensors (Step 162). For example, controller 90 may monitor and receive signals from engine 18 and a variety of temperature, pressure, flow, speed, and other sensors. Controller 90 may determine whether an engine off signal has been received (Step 164). When controller 90 determines that an engine off signal has been received (Step 164, Yes), controller 90 may proceed to Step 166. When controller 90 determines, however, that an engine off signal has not been received (Step 164, No), controller 90 may return to Step 146.

In step 166, controller 90 may determine whether first oil pump 32 is off (Step 166). When controller 90 determines that first oil pump 32 is off (Step 166, Yes), controller 90 may start first oil pump 32 (Step 168). When controller 90 determines, however, that first oil pump 32 is not off (Step 166, No), controller 90 may proceed directly to Step 170. In step 170, controller 90 may open second control valve 44 and close first and third control valves 42, 46 (Step 170). First oil pump 32 may supply oil to cool turbochargers for time t₄ (Step 172). For example, controller 90 may keep second control valve 44 open and allow oil from first oil pump 32 to flow through, lubricate, and cool first, second, and third turbochargers 82, 84, 86 for a fourth amount of time t₄. After time t₄ has elapsed, controller 90 may stop first oil pump 32 (Step 174). Thus, controller 90 may perform soak-back operations by supplying oil to lubricate and cool first, second, and third turbochargers 82, 84, 86 for a fourth amount of time t₄ after engine 18 has been turned off. In one exemplary embodiment the fourth amount of time t₄ may be about 35 minutes.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed lubrication system without departing from the scope of the disclosure. Other embodiments of the lubrication system will be apparent to those skilled in the art from consideration of the specification and practice of the lubrication system disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents. 

What is claimed is:
 1. A lubrication system for an engine, comprising: an oil pump configured to lubricate the engine; a valve configured to direct oil from the oil pump to a fuel pump associated with the engine; and a controller configured to: determine an operating speed of the engine; and adjust the valve to selectively direct the oil to the fuel pump based on the operating speed.
 2. The lubrication system of claim 1, wherein the controller is configured to: open the valve when the operating speed of the engine is less than or about equal to a threshold operating speed; and close the valve when the operating speed of the engine exceeds the threshold operating speed.
 3. The lubrication system of claim 2, wherein the valve is a first valve and the lubrication system further includes: a second valve configured to direct the oil from the oil pump to a turbocharger associated with the engine; and a third valve configured to direct the oil from the oil pump to the engine.
 4. The lubrication system of claim 3, wherein each of the first valve, the second valve, and the third valve is a two position solenoid valve.
 5. The lubrication system of claim 3, wherein the controller is configured to direct a first flow of oil by opening the first valve and closing the second valve and the third valve.
 6. The lubrication system of claim 5, wherein the controller is configured to: direct a first portion of the first flow of oil to the fuel pump; and direct a second portion of the first flow of oil to actuate an exhaust gas recirculation valve.
 7. The lubrication system of claim 6, wherein the controller is further configured to stop the oil pump when the operating speed of the engine exceeds the threshold operating speed.
 8. The lubrication system of claim 3, wherein the controller is configured to direct a second flow of oil to the turbocharger by opening the second valve and closing the first valve and the third valve.
 9. The lubrication system of claim 8, wherein the controller is configured to: determine whether the engine has been turned off; start the oil pump when the engine has been turned off; and direct the second flow of oil to the turbocharger.
 10. The lubrication system of claim 3, wherein the controller is configured to direct a third flow of oil to the engine by opening the third valve and closing the first valve and the second valve.
 11. The lubrication system of claim 10, wherein the controller is configured to: determine a first amount of time for which the engine has been off; and direct the third flow of oil to the engine, when the first amount of time exceeds a threshold amount of time.
 12. A method of operating a machine, comprising: supplying oil for lubrication, using a first oil pump associated with the machine; lubricating an engine associated with the machine using the oil; starting the engine; determining an operating speed of the engine; and adjusting a valve to selectively direct the oil from the first oil pump to a fuel pump associated with the engine based on the operating speed.
 13. The method of claim 12, wherein adjusting the valve includes: opening the valve when the operating speed is less than or about equal to a threshold operating speed; and closing the valve when the operating speed exceeds the threshold operating speed.
 14. The method of claim 13, wherein opening the valve includes: directing a first portion of a first flow of oil from the first oil pump to the fuel pump; directing a second portion of the first flow of oil to an exhaust gas recirculation valve; and actuating the exhaust gas recirculation valve using the second portion.
 15. The method of claim 14, wherein closing the valve further includes supplying the first flow of oil, using a second oil pump.
 16. The method of claim 15, further including: lubricating the engine for a first amount of time; lubricating a turbocharger associated with the engine for a second amount of time; and lubricating the fuel pump for a third amount of time.
 17. The method of claim 16, wherein lubricating the turbocharger includes: directing a second flow of oil from the first oil pump to the turbocharger; and stopping the second flow of oil after the second amount of time.
 18. The method of claim 17, wherein lubricating the engine includes: determining a time interval for which the engine had been off; directing a third flow of oil from the first oil pump to the engine, when the time interval exceeds a threshold time interval; and stopping the third flow of oil after the first amount of time.
 19. The method of claim 18, further including: determining whether an engine off signal has been received; turning off the engine in response to the engine off signal; directing the second flow of oil to the turbocharger; and stopping the second flow of oil after a fourth amount of time.
 20. A mobile machine comprising: an engine configured to propel the machine; at least one turbocharger configured to supply air to the engine; at least one exhaust gas recirculation valve configured to recirculate exhaust in the engine; a fuel pump configured to supply fuel to the engine; a sump configured to store oil for lubrication; an oil pump configured to pump the oil from the sump; a manifold configured to receive the oil from the oil pump, the manifold including: a first valve configured to direct the oil to the fuel pump and the exhaust gas recirculation valve; a second valve configured to direct the oil to the turbocharger; and a third valve configured to direct the oil to the engine; and a controller configured to adjust the first valve to selectively direct the oil to the fuel pump based on an operating speed of the engine. 